Photochemical Hydrogen Generation Using Nitrogen-Doped TiO2-Pd Nanoparticles: Facile Synthesis and Effect of Ti3+ Incorporation

Crystalline nanoparticles of anatase phase nitrogen-doped TiO2 (N-TiO2), boron and nitrogen codoped TiO2 (B-N-TiO2), and undoped TiO2 (TiO2) were synthesized by a facile xerogel method followed by reduction in a glycol medium to forcibly create Ti3+ ions (self-doping) in them (R-N-TiO2, R-B-N-TiO2, and R-TiO2, where R stands for reduced) and studied their photocatalytic activity for hydrogen generation from water. A clear red shift of the absorption edge and stronger absorption in the visible region was observed for both reduced and unreduced N-TiO2 and B-N-TiO2 compared to the other samples. The presence of bonded nitrogen in the N-doped samples was evidenced from their N1s X-ray photoelectron spectra. Photocatalytic activity for hydrogen generation using sunlight-type radiation showed enhanced activity for the reduced and doped samples compared to pristine TiO2. The enhanced photocatalytic activity of the R-N-TiO2 for hydrogen generation is attributed to the enhanced light absorption resulting from the narrowing of the band gap caused by the contribution of anion levels near the conduction band and 2p levels of N near the valence band of TiO2. A significant enhancement of photocatalytic activity was observed when Pd metal was present as a cocatalyst due to the efficient separation of photogenerated charge carriers in these nanoparticles.